According to my handy-dandy stitch dictionary, this is also called the “open chain stitch” or “Roman chain stitch”. This is a nice, relatively simple, geometric decoration. Because it has a straight edge, you can work it right on top of a machined hem to hide the machine stitches. (I believe in cheating.)
Begin by pushing a needle with a knotted thread up from the back of the fabric.
insert the needle directly above where the thread comes through the fabric, and pass it diagonally behind the fabric. Push it up in line with the original thread and wrap the thread beneath the needle.
As you're pulling your first stitch through and taut, immediately begin taking the second. Use your needle to catch the loop of the first stitch (forming the final corner of the square), and take another diagonal stitch beneath the fabric. Again, wrap your thread under the needle as it emerges.
Lather, rinse, and repeat.
This is all great, but what do you do when you want to stop? First, start a final stitch.
take a tiny stitch across the first corner of the square, and pass the needle under the fabric to the second corner. Catch the thread loop with the needle.
Take a tiny stitch across the second corner, and push the needle through the fabric.
In back, tie off your thread. I tie mine around an existing stitch, so nothing shows on the right side. I have a hem here, so I'm taking a big stitch inside it. When I cut my thread, the tail will be buried and hidden.
I think I learned the thing about tying the thread off over another thread from an aunt (great or just normal, I can’t recall). I’m just as positive that another aunt taught me that there were no knots in embroidery, ever. I don’t claim to be an embroideress, but I do think stitches are less likely to pull out if you tie off your threads, so I do.
Also, you can see the back of the stitch here – it’s a series of diagonal stitches. This is nifty, because it’s hiding my stitch line in front and binding my seam allowance in back. Two jobs done with one stitch – I love that!